Graves' disease is an autoimmune disorder caused by pathogenic thyroid stimulating antibodies (TSAb) that mimic TSH in activating the TSH receptor (TSHR). The resulting hyperthyroidism can be treated but there is no cure. A critical barrier to studying its pathogenesis, as well as investigation of novel therapies, is that Graves' disease only occurs in humans. Therefore, the development of a mouse model that spontaneously develops pathogenic TSHR antibodies would represent a highly significant advance, providing insight into the pathogenesis of Graves' disease and facilitating investigation of potential approaches for specific immunotherapy for cure, rather than treatment of this common human disease. By crossing transgenic mice that express the human TSHR A-subunit in the thyroid to another mouse strain that spontaneously develops thyroiditis, we have developed the first animal model, hTSHR/NOD-H2h4 mice, that spontaneously develops pathogenic TSAb. Our first aim will be to optimize and characterize the hTSHR/NOD-H2h4 mouse model. We will complete back-crossing to the parent strain for a total of 10 generations to ensure that hTSHR/NOD-H2h4 mice have 100% of NOD-H2h4 background genes. We will then determine the time course of pathogenic TSHR antibody generation, titer and maintenance of levels, as well as characterize the model for thyroid function, thyroid histology and the full compendium of thyroid autoantibodies. Our second aim is to investigate factors that may influence the spontaneous development of pathogenic TSAb in this model including the role of central tolerance by measuring intrathymic expression of the human TSHR A-subunit (and the other thyroid antigens). We will also assess the influence of regulatory T cells on TSHR Ab development, determine epitopes recognized by T-cells, as well as the influence of environmental factors (vitamin D3 and selenium) on TSAb levels. Our third aim is to suppress the development and, particularly on-going production, of TSAb. Approaches to be used will be injecting TSHR A-subunit protein, an approach that may cause deviation of TSAb to a benign, non-pathogenic form. We will also attempt to induce tolerance to the TSHR by a number of approaches, including injecting immature dendritic cells pulsed with purified TSHR A-subunit protein, as well as by blocking the second signal between T-cells and antigen presenting cells.